The U.S. Federal Communications Commission says it will act by the end of the year on a White House-appointed panel's recommendation to have federal agencies share 100MHz of spectrum with commercial users.

The FCC will take steps this year to carry out recommendations from the President's Council of Advisors on Science and Technology (PCAST) for spectrum-sharing in the 3.5GHz band, Chairman Julius Genachowski announced on Wednesday. The set of frequencies between 3550MHz and 3650MHz is currently used in radar systems but could be shared with other wireless services if they were implemented through small cells, the panel said in its report, issued in July. PCAST called on the FCC and the National Telecommunications and Information Administration (NTIA) to start work immediately on sharing this band and one other of the agencies' choice.

PCAST identified this band as the spot where federal users could most quickly start sharing spectrum. The group proposed governing the spectrum in a similar way to the so-called "white spaces" between TV channels, where devices have to be registered and refer to a database telling where the primary users of the spectrum reside. In areas where they might interfere with the primary users, they need to back off to prevent this. However, the group left the choice of technical approach to regulators.

The panel was formed to help find more efficient uses for wireless spectrum used by the federal government, as part of an effort to make more frequencies available for wireless data. It said new technologies, including small cells and smarter radios, have made it easier for more than one type of use to coexist on the same frequency. The report identified 11 blocks of spectrum, including the 3.5GHz band, to investigate for possible sharing. Taken together, those bands add up to nearly 1.5GHz of spectrum.

The 3.5GHz band was fingered for possible exclusive-use licenses in a report issued last year by the NTIA, which oversees federal use of spectrum. However, in order for the government to keep using the spectrum for radar systems, other uses would have had to be blocked for about 200 miles inland from all U.S. coastlines, leaving out a majority of the country's residents, PCAST said in its report. A spectrum-sharing system could dramatically shrink or eliminate those exclusion zones, the group said.

Because of its high frequency, the 3.5GHz band would be better suited to fixed wireless Internet service than to mobile, according to Farpoint Group analyst Craig Mathias. Frequencies in this band have been used for fixed WiMax networks, and service providers that take advantage of the shared band might also use that technology, he said. Mathias believes that even if the government chooses to make the spectrum shared, it will auction off commercial licenses for that shared access.

The 3.5GHz band may be an even better place for the white-spaces approach than TV channels, despite TV spectrum having much longer reach, Mathias said. In urban areas there are few TV frequencies available for white-spaces use because there are too many active TV stations saturating the airwaves, he said. The 3.5GHz band is much less crowded, he said.

The push for frequency-sharing, a departure from the federal government's typical way of managing its spectrum, has drawn some criticism. CTIA, the main industry group for U.S. mobile operators, has said exclusive licensing is the best way to manage frequencies. And on Thursday, Republican lawmakers also said the government should hand over more spectrum to commercial operators instead of asking them to share it.